Carburetor



Qct. 1, 1935. s. -F. HUNT 7 2,015,753

' 'cARBuRETpR Ori'ginhlFiled Jan. 25., 1953 s Sheets-Sheet 1 v I INVENTOR. ScoH F Hunf.

ATTORNEY.

1, 1935. s. F. HUNT 2,015,753

cmaunmon Original Filed Jan. 25, 1933 3 Sheets-Sheet 2 g INVENTOR. 560%? E Hum.

Get. 1, 1935. s. F. HUNT CARBURETOR Original Filed Jan. 25, 1933 3 Sheets-Sheet 3 23 E 0 W a v 6 .M. M vi: 45 x .n l m A z a V 4110mm Patented Oct. 1, 1935 UNITED STATES Scott 1. Hunt, South Bend, ma, assignor to Bendix Aviation Corporation, South Bend, Ind., i a corporation of Delaware Applicationlanuary 25, 1933, Serial No. 653,519 Renewed October 22, 1934 14 Claims. (Cl. 123119) This invention relates to control mechanisms for internal combustion engine carburetors, and has for its principal object the provision of an automatic choke valve control mechanism arranged ,5 to, govern the degree of opening of the choke valve as a function of temperature when the engine is running and to close the valvewhen the engine stops.

Internal combustion engines using as fuel a 10 mixture of liquid fuel and air, require a richmixture when starting and a leaner when the engine is idling during the warming up period. Certain prior art devices, of which the copending application of Hunt andOlson, Serial No. 575,025, 15 filed November 14, 1931, is an example, provide for holding the choke valve of the carburetor closed to form a starting mixture and, when the engine begins firing,further provides for opening the choke valve andgrading down the rich- 20 ness of the mixture as a function of engine tem- 25 is not necessary to close the choke valve every time the engine is started. Other engines require a very rich mixture to start regardless of temperature and it is necessary to close the choke valve each time the engine is started.

30 The present invention improves upon the devices of the prior art by providing for closing the choke valve each time the engine is stopped regardless of temperature.

Internal combustion engines must be idled at a higher speed when they are cold than when they are warm, and the present invention also provides an automatic control of the throttle to set it in starting position when the engine stops, to set it for a fast idle when the engine is cold 40 and to reset it for a slow idle when the engine has reached its normal operating temperature.

My invention will be best understood from the detailed description and claims which follow,reference being had to the accompanying drawings in which I haveshown a preferred embodiment of the invention byjway of example and in which:

Figure 1 is an elevational view of a carburetor with the control mechanism of the invention as- 5 sociated therewith; p I

Figure 2 is a cross sectional view through the control unit showing the same inthe position it assumes during the normal running of the engme;

55 Figure 3 is a view sim lar o Figure 2 showmg the mechanism in position to idle the engine when it is warm;

Figure 4 is a similar view showing the mechanism in position for starting the engine;

Figure dis a similar view of a modified form 5 l of the invention; a

Figure 6 shows another modification, which is arranged to trigger lock the choke valve open and closed;

Figure 7 shows another form of trigger arrangement; i t

Figure 8 shows a modified form of trigger and throttle controlled unlocking lever therefor;

Figure 9 shows a modified form of control mechanism including a throttle control shownin position for idling the engine at slow speed;

Figure 10 is aview similar to Figure 9 showing the mechanism in position to start the engine when it is cold;

Figure 11 is a view of the mechanism shown in Figure 9 in position for fast idling of the motor;

Figure 12 is across sectional viewtaken along the line l2-|2 of FigurelO looking in the direction of the arrows; and v i a Figure 13 shows a modified form of the control mechanism shown in Figure 9 including a trigger for controlling the choke valve.

Referring now to the drawings in more detail, in Figure 1 I have shown a carburetor l0 having an air pressure operated choke valve l2 and a throttle l4. Carburetor ill is shown as a plain tube down draft carburetor, this type being shown by wayof example only as the invention may be applied to any preferred type of carburetor. The control unit, indicated generally at It, includes the invention, the unit. being shown as separate from the carburetor structure for the sake of clarity. In practice the control mechanism may be incorporated in the carburetor proper within the teachings of the invention. As shown the control mechanism includes a thermostat l8 of ,known construction, preferably a bimetallic element located near the-exhaust manifold of the engine, having a shaft 20 which carries an arm 22 that is keyed thereto. A rod 24 connects the 5 free end of the arm to the choke valve thereby to enable the thermostat to control the degree of opening of the valve as a function of temperature.

The control unit includesa second shaft 26 to which an arm 28 is fixed; A rod 30 connects the 60 free end of arm 28 with the free end of an arm 32 that is fixed upon the shaft of the throttle so that the shaft 26 is rotated by rotation of the throttle. The control mechanism also includes a piston 34 which is fitted in a cylinder and urged upwardly nected to the intake manifold of the engine so that the piston is drawn downwardly against the tension of spring 36 when the engine is firing.

A lever 38 is journalled for rotation on shaft 26 and connected by rod 40 to the piston 34 to be operated thereby. An arm 42 is keyed upon thermostatshaft 28 and carries a pin 44 which bears against the arcuate cam surface of lever 38. When the engine ceases firing spring 36 raises piston 34 and moves lever 38 clockwise around appear.

. A latching trigger 50 is pivotally mounted upon lever '38 and urged in a clockwise direction around its pivot by a suitable spring 5|, this movement being limited by an car 52 on the trigger and an ear 53 on the lever. An arm 54 is keyed upon throttle shaft 26 and carries an adjustable screw 55 which is arranged to strike an ear 56 and rotate the trigger against the tensionof spring 5| as the throttle is closed.

When the motor is not running and is cold, to startit, the throttle is opened part way and the control mechanism is positioned as shown in Figure 4. Pin 44 is registered with recess 48 and the trigger is released and held against the pin by spring 5| which is not strong enough to move the pin out of the recess. The engine is cranked and as soon as it begins to fire the piston rotates lever 38 away from the pin and the choke valve isheld closed by the tension in the thermostat and the tension of spring 5| acting through trigger 50. As soon as the throttle is closed to idle the engine, as it should be immediately the engine fires, screw 55 rotates the trigger into the position in which it is shown in Figure 3, and the thermostat alone controls the choke valve. As the engine warms up the tension of the thermostat decreases and allows the choke valve-to be opened by the air pressure on it, pin 44 moving over surface 46 into the position in which it is shown in Figure 3. As soon as the throttle is again opened to accelerate the engine, screw 55 moves away from ear 56 and spring 5| moves trigger 50 into its normal position, shown in Figure 2. Pin 44 strikes against the end of the trigger to lock the choke valve open. In this position lever 42, pin 44, trigger 58 and lever 38 together lock piston 34 down in its operated position and it is not vibrated by variations in pressure occurring in the intake manifold during the normal operation of the engine. When the engine is stopped, and the throttle closed, screw 55 unlatches the trigger and spring 36 rotates lever 38. This rotation causes surface 46 to cam pin 44 into recess 48 thereby to close the choke valve even though there is no tension in the thermostat.

Arm 54 is provided with an ear 58 which overhangs lever 38 and when the throttle is moved to wide open position, in which it is shown in Figure 2, ear 58 moves lever 38 into its operated position. Pin 44 is thus disengaged from the recess and the choke valve may be opened to permit a flooded condition of the engine to be corrected.

In the modification shown in Figure 5 arm 68 is 'mostat when the throttle is 2,016,753 therein by a spring 36, the cylinder being con clamped upon shaft 26 by suitable means 62, and this arm is provided with an ear 64 which corresponds in function to screw 55, and an car 66 which corresponds in function to ear 58. A trigger 68 is pivotally secured to lever 38 and is pro- 5 vided with a stop 16 which engages the lever to limit the movement of the trigger with respect to the lever. Spring" is connected between the lever and the trigger to rotate the trigger to bring stop ll against the lever. Lever 42 on the thermostat shaft carries a pin or roller 12 which rests against the end of the trigger and the edge of lever 38 when the choke valve is open to lock the valve in that position, and to lock the lever in its operated position. When the choke 5 valve is closed by the cam action of lever 38 pin 12 registers with a races 13 in trigger 68 to lock the valve closed. Ear 64 unlatches the trigger to restore the choke valve to the control of the therclosed to idle the engine. 4

In the modification shown in Figure 6 lever 38 floats upon shaft 26 as before and is arranged to be rotated thereon by the piston. Thermostat shaft 28 carries a lever 42, keyed thereto, and this lever is provided with a pin or roller 43 which engages the cam surface 46 of the lever. A latch I6 is pivotally mounted upon lever 38 and provided with an ear 11 against which a leaf spring I8 bears to rotate the latch until the ear strikes 30, the lever. When the choke valve is open, pin 43 bears against the end of the latch and against lever 38 to lock the valve. Throttle shaft 26 carries an arm 19 into which is threaded a screw 86 which engages the latch 16 when the throttle is closed, to unlatch the choke valveso that the piston spring can close it. Arm 19 also carries an ear 8| which engages the lever, as the throttle is moved to wide open position, to move the lever and piston to operated position. When lever 38 is in its normal or unoperated position, in which it is shown in dotted lines in the figure, and the choke valve is closed, pin 43 again engages the end of the latch and lever 38 to lock the valve closed.

In the modification shown in Figure 7 trigger 82 is pivotally mounted upon lever 38 and is provided with a stop pin 83 which registers with a recess in the lever. Spring 84' is hooked between the trigger and the lever and is tensioned to seat the pin in the recess. The pin 43 on thermostat arm 42 engages the end of the trigger to lock the choke valve open. An arm 85 is clamped upon shaft 26 by a bolt 86 and when the throttle is closed the head of the bolt. engages the trigger and rotates it to release pin 43. The cam end of lever 38 opens the choke valve as the piston spring restores the lever to its unoperated position. When the throttle is moved into wide open position the nut on bolt 86 engages lever 38 to move it into its operated position. 80

In the modification shown in Figure 8, a trigger 88 is pivotally mounted upon lever 38 and urged in a counterclockwise direction thereon by a spring 92. The trigger is provided with stop ears 8! and 89 which engage an ear 8!) on the lever to limit the movement of the trigger. Thermostat arm 42 carries a. roller 43 which bears against a short radius cam surface on the trigger. When the choke valve is open roller 43 engages the surface 9| adjacent to stop 63 and the line of thrust on the trigger falls between the pivotal connection of the trigger to lever 36 and the stop, and the tension of the piston spring aids sprirg 8| in keeping stop 89 against stop 88.- The choke valve is locked open. An arm 94 is clamped upon throttle shaft 26 and carries a screw which engages, stopll, when the throttle is closed, to rotatetriggerf" against thetenslon of spring 82 and bring stop 31 into engagement with ear 00. Stop pushes roller 43 to the left during this rotation of the trigger to bring the line of thrust of lever 42 on the trigger between the" pivotal connection of the same and shaft 26, to unlock the choke valve so that the tension of the piston spring can close the valve. With the valve closed, trigger 80 bears against the roller at such an angle that the tension of the piston spring maintains the valve closed. When the throttle is moved to wide open position, the nut on the bolt that clamps arm 04 upon shaft 26 engages lever 38 to move the same to its operated position thereby to bring the center of arcuate surface 9| into substantial alignment with the axis of shaft 20 and the chokevalve may be opened by the air pressure upon it under the control of the thermostat. When the engine is firing the piston performs the same function to permit the choke valveto open.

In the embodiment of the invention shown in Figures 9, i0, 11, and 12, I have shown a control for, automatically setting the throttle in starting position, when the engine is not running and is cold, for setting the throttle to give a fast idle during the warming up period, and to reset the throttle for a slow idle after the engine is warm and the choke valve is fullyopened. This feature, broadly speaking, is an improvement upon the disclosure of the co-pending application of Hunt, Serial No. 630,274,filed August 24, 1932. In this arrangement lever 38 floats uponshaft 26 and r lever 42 is keyed to shaft 20 and is provided with a roller which engages a cam surface on lever 38 as before. A plate I00 is keyed to shaft 20 and provided with a cam boss IM and with an arcuate surface I02 whose center coincides with the axis of shaft 20. A second plate I03 floats upon shaft 20 and is adjacent to plate I00. A spring I 04 is connected between plates I00 and I03 and is tensioned to keep plate I03 normally centered on plate I00. Plate I03 isprovided with an arcuate cam surface I09 which centers on the axis of shaft 20 and out of one end of which rises a stopboss I05. An arm I06 is fixed upon shaft 26 and carries a screw I01 which is adapted to engage cam surfaces IOI, I02, I09, and the stop I05. In the operation of the device, when the engine is not running and the-choke valve is closed by the combined action of I the thermostat, when cold, and

, on shaft 26 to release the choke valve by disengaging the roller from the recess'in lever 38.

The choke valve opens under the control of the they are shown inFlgure ll. ,Screw I01 e ages stop boss I05 andplate I03 ispulled of! center as plate I00 is moved, bylthe choke valve moving to wide open position. 1 Spring I04 is tensioned. As soon as the throttle is opened to accelerate the engine, screw I01 is disengaged from boss I05 and spring I04recenters plate I03 upon plate I00. When the throttle is subsequently closed screw I01 registers with cam surface I02, which is positioned topermit the throttle to close fully and a slow idle of the engine results. The edge of lever 30 engaged by roller 43 is shaped to bear upon roller43 at a point aligned with the axes of the roller and shaft 20, when the choke valve, is fully opened, and because of this dead center position the choke valve is locked open by the piston spring. Lever 42 also serves to lock the piston in itsoperated position so that it will not be vibrated by the variations in pressure occurring in the intake manifold during the operation of the engine. Arm I06 is provided with a pin I03 which engages lever 30, when the throttle is in wide open position, to move the lever to its operated position.

In the modification shown in Figure 13 the automatic throttle control is combined with the trigger type automatic choke shown in the prior figures. In this modification lever 30 carries aItrigger IIO, pivotally connected thereto and rotated into latching position by spring III. 30

Arm I06 carries a subarm I I2 which engages the cams of the throttle control in lieu of a screw. Arm I06 also carries a screw II3 which engages the trigger to unlatch the same when the throttle is fully closed. The operation of the device will beapparent from the foregoing and need not be described in detail herein.

While I have chosen to show my invention by illustrating and describing a preferred embodiment of it, I have done so by way of example only as there are many modifications and adaptations that an be made by one skilled in the art within the teachings of the invention.

What is claimed is:

1. ,In a control mechanism for an internal 4 combustion engine carburetorhaving a choke valve and a throttle, a thermostat for controlling the degree of opening of the choke valve as a function of temperature, means for locking said choke valve open, andnieans for unlocking said 5 locking means each time the throttle is closed.

2 In a control mechanism for an ,internal combustion engine carburetor having a choke valve and a throttle, a thermostat for controlling the degree of opening of, the choke valve as a 5 function of temperature, meansfor locking said choke valve open, means for unlocking said locking meanseach time the throttle is closed, and means for closing the choke valve when the engine stops. p 6

3. In a control mechanism for an internal combustion engine carburetor having a choke valve and a throttle, a thermostat for controlling the degree of opening of the choke valve as a function of temperature, means including a 6 trigger for locking said choke valve open, means for moving said trigger to unlock the choke valve each time the throttle is closed, and means for closing the choke valve'when the engine stops.

4. In a control mechanism for an internal: combustion engine carburetor having a choke valve and a throttle, a thermostat for controlling the degree of opening of the choke valve as, a function of temperature, means including a trigger for locking said chokeivalve open, alev er'l fixed to and moved with the throttle for moving said trig er to unlock the choke valve each time the throttle is closed, and'means for closing the choke valve when the engine stops.

5. In a control mechanism for an internal combustion engine carburetor having a choke valve and a throttle, a thermostat for controlling the degree of opening of the choke valve as a function of temperature, an arm on said thermostat moved with the choke valve, a lever engaging said arm when the choke valve is closed to lock the same closed, means for disengaging said lever from the arm when the engine fires to permit the choke valve to open under the control of the thermostat, a trigger on said lever engaging said arm when the choke valve is open to lock the same open, meansfor moving said trigger to unlock the choke valve when the throttle is closed, and means for moving said lever to engage the arm and close the choke valve when the engine stops.

6. In a control mechanism for an internal combustion engine carburetor having a choke valve and a'throttle, a shaft, means connecting the shaft tothe choke valve, an arm on the shaft, a second shaft, a lever floating on said second shaft, means on .said lever registered with .said arm to lock the choke valve closed, means actuated by vacuum in the engine for moving said lever to unlock said arm, a thermostat connected to said first shaft for regulating the degree of opening of the choke valve as a function of temperature, a trigger on said lever engaging said arm to lock the choke valve open, means on said second shaft engaging said trigger when the throttle is closed to unlock the choke valve, and means effective when the engine stops for moving said lever to close the choke valve.

7. In a control mechanism for an internal combustion engine carburetor having an air pressure actuated choke valve and a throttle, a pivoted arm connected to the choke valve, a pivoted lever, a spring for moving the lever in' one direction to engage the armand close the choke valve for starting the engine, a piston for moving the lever out of engagement with the arm to permit thechoke valve to open, a thermostat connected to control the degree of opening of the choke valve as a function of temperature, a latch pivoted on said lever and engaging said arm to lock the choke valve open, and means for disengaging the latch from the arm when the throttle is closed to permit said spring to close the choke valve when the engine stops.

8. In a control mechanism for an internal combustion engine carburetor having an air pressure actuated choke valve and a'throttle, a pivoted arm connected to the choke valve, a pivoted lever, a spring for moving the lever in one direction to engage the arm and close the choke valve for starting the engine, a piston actuated by vacuum in the engine for moving the lever out of engage: ment with the arm to permit the choke valve to open, a thermostat connected to control the degree of opening of the choke valve as a function of temperature, a trigger pivoted to said lever, a spring for rotating the trigger, stop means for limiting said rotation to position the trigger to engage the arm and lock the choke valve open, and means for diseng ing the trigger from the arm when the throttle is closed to permit said first spring to close the choke valve when the engine stops.

9. In a. control mechanism for an internal combustion engine carburetor having a choke valve and a throttle, a pivoted arm connected to the choke valve, means engaging the arm for locking the choke valve closed and for locking it open, means for releasing the arm from closed position when the engine fires, a thermostat for controlling 5 combustion engine carburetor having a choke valve and a throttle, a shaft, an arm fixed on said shaft and connected to the choke valve, means engaging the arm for locking the choke valve closed and for locking it open, means for releasing the arm from closed position when the engine fires, a thermostat for controlling the degree of opening of the choke valve as a function of temperature, cam means on said shaft fixed with respect to said lever, and a pivoted lever connected to the throttle and engagingsaid cam means to set the throttle in starting, fast idle and slow idle positions respectively as the choke valve is closed, partly open, and fully open.

11. In a control mechanism for an internal combustion engine carburetor having a choke valve and a throttle, a shaft, means connecting the shaft to the choke valve, an arm fixed upon the shaft, means engaging the arm for locking the choke valve closed and for looking it open, means for releasing the arm from closed position when the engine fires, a thermostat for controlling the degree of opening of the choke valve as a function of temperature, a plate fixed on said shaft, two cam surfaces on said plate located at different radial distances from the axis of said shaft, a sec- 0nd plate 'journalled on said shaft and disposed adjacent to the first plate, a cam surface on said secondplate located intermediate the cam surfaces on said first plate, and means connected to the throttle and engaging the cam surface most distant from the axis of the shaft when the choke valve is locked closed, engaging the intermediate cam when the choke valve is opening under the control of the thermostat and engaging the near cam when the choke valve is locked open to set combustion engine carburetor having-a choke valve and a throttle, a shaft, means connecting the shaft to the choke valve, an arm fixed upon the shaft, means engaging the arm to lock the choke valve closed and to lock it open, vacuum actuated means for releasing the arm from closed position "when the enginefires, a thermostat for controlling the degree of opening of the chokevalve as a function of temperature, cam means on the shaft fixed with respect to the arm, a pivoted lever engaging said cam means and connected to the throttle to set it to starting position, fast idle position and slow idle position respectively as the choke valve is closed, partially open and fully open, and means for restoring the choke valve and throttle to starting position when the engine stops.

13. In a control mechanism for an internal combustion engine carburetor having a choke valve and a throttle, a shaft, means connecting the shaft to the choke valve, an arm fixed upon the shaft, 9. pivoted lever engaging the arm to lock the choke valve closed, vacuum actuated means for releasing the arm fromclosedposition when the engine fires, a thermostat for controlling the degree of opening of the choke valve, as a function of temperature, means on said lever for locking the choke valve open, cam means fixed on said shaft, a throttle lever engaging said cam means to set the throttle in starting position, fast idle position, and slow idle position, respectively, as the choke valve is closed, partially open and. fully open, means on said throttle lever for releasing said locking means when the throttle is closed, and means for restoring the choke valve and throttle to starting position when the engine stops.

14. In a control mechanism for an internal combustion engine carburetor having an air pressure actuated choke valve and a throttle, a shaft,

mounted on the shaft adjacent to said first cam,

spring means for keeping said second cam centered on the first, and an arm connected to the throttle and engaging said cams to set the throttle for starting, fast idling, and slow idling respectively as the choke valve is closed, partly open and fully open.

SCOTT F. HUNT. 

